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OP38 Ophthalmology
Pediatric Ophthalmology Toronto Notes 2019
Retinal Zones
Management
• strabismus
■ correct with glasses for accommodative esotropia
■ occlusion therapy (see below)
■ surgery: recession (weakening) – moving muscle insertion further back on the globe; or resection
(strengthening) – shortening the muscle
■ botulinum toxin for single muscle weakening
■ after ocular alignment is restored (glasses, surgery, botulinum toxin), patching is frequently
necessary to maintain vision until ~8 yr of age
■ there is no proven value for vision training in the treatment of strabismus or amblyopia
• anisometropia
■ the more emmetropic (normal refraction) eye receives a clear image, while the less emmetropic eye
receives a blurred image; input from the blurred eye is cortically suppressed and visual pathway fails
to develop normally treat with glasses to correct refractive error
■ patching is required if visual acuity difference persists after using glasses for 4-8 wk
• deprivation: treat underlying cause
• amblyopiatreatmentlesssuccessfulafterage8-10yr,butatrialshouldbegivennomatterwhatage
■ prognosis: 90% will have good vision restored and maintained if treated before age 4
Occlusion Therapy
• patchingthegoodeyetoforcethebraintousethenon-dominanteyeandredevelopitsvision • atropinecycloplegicdropstoimpairaccommodationandblurvisionofthebetterseeingeye
Risks
• permanentlossofvisionintheaffectedeye
• possibilityofinjuryto“remaining”goodeye(e.g.occlusionamblyopia)
• safetyglassesorpolycarbonatelensesrecommendedifvisualacuityinworseeyeis<20/50 • lossofstereopsis
Leukocoria
Definition
• whitereflex(redreflexisabsent)
• thepresenceofleukocoriawarrantsurgentreferraltoanophthalmologist
Differential Diagnosis
• cataract
• retinoblastoma
• retinalcoloboma
• ROP
• persistenthyperplasticprimaryvitreousorpersistentfetalvasculature • Coat’sdisease(exudativeretinaltelangiectasis)
• toxocariasis
• RD
Retinoblastoma
Definition
• intraocularmalignancythatrapidlydevelopsfromimmaturecellsoftheretina
Epidemiology
• mostcommonprimaryintraocularmalignancyinchildren • incidence: 1/15,000
• unilateral(2/3)orbilateral(1/3)
• malignant–directorhematogenousspread
Etiology
• sporadicorgenetictransmission;screeningofsiblings/offspringessential
• inheritedformslikelytobebilateral
• oftencausedbymutationsinRB1,thefirsttumoursuppressorgenediscovered,andlesscommonlyby
amplifications of MYCN, an oncogene
Diagnosis
• oftenpresentswithleukocoriaand/orstrabismus
• otherssigns:redeye,eyeenlargementifadvanceddisease
• U/SorCTscanmaydemonstratecalcifiedmass(presentinmostcases)
Treatment
• radiotherapy,chemotherapycombinedwithlaser,cryopexy,and/orenucleation
• Zone I: circle with radius twice the distance from the disc to the macula (most difficult to treat)
• Zone II: annulus from zone I to nasal extent of retina (nasal ora serrata)
• Zone III: remaining retina
Zone II
Zone I
Optic
nerve Macula
Zone III
Figure 27. Zones of the retina in ROP